References
- Wundt , W. 1912 . An Introduction to Psychology , 43 – 63 . London : George Allen & Co., Ltd. .
- Wundt , W. 1907 . Outlines of Psychology , 16 – 30 . New York : G. E. Stechert & Co. . 31–40, 83–101, 176–181 and 188–203. 3rd revised English edition